This invention generally relates to apparatus and methods for recording and projecting images on curved screens in a manner that imparts to an audience a sense of immersion in the projected scene. The screen is usually a segment of a spherical dome, with a large portion of the segment located below the horizontal viewing line of an audience. For a relatively large audience, the viewing lines are optimized for the center, or xe2x80x9csweet spot,xe2x80x9d of the audience. When the invention is used in a setting such as a theme park attraction, the audience may be suspended relative to the segment to give the guests the feeling of flying over the projected scene. The scenes may be landscapes such as mountain valleys, orange groves or pine forests. The scenes may be the buildings of a city, or surfers riding ocean waves. The invention imparts to the audience the feeling of immersion in the projected scene.
Curved projection screens, such as domes found in IMAX systems, have generally been placed in front of and overhead an audience, with much of the projected scene above the horizontal sight lines of the audience. Because the goal of the present invention is to create a feeling of being within and over a scene, the technology that presently exists for projecting a scene to an upward looking audience is not satisfactory.
The images that are projected may be filmed, video taped, recorded digitally or recorded in any other manner, or may be created artificially using animation, computer generated graphics or any other method. If recorded on film, as by a helicopter carrying a camera system, then the system of the present invention gives the audience the perception that they are located relative to the projected scene in approximately the same position as the camera lens was positioned relative to the scene it was recording.
In order to appear realistic, the images that are recorded on film by a camera must appear, when projected on the screen to the theater viewer, to be in the same relative positions and at the same relative angles as they appeared to the camera lens while being filmed (scene angles). The field of view of the projected image must substantially match the field of view of the image as observed by the camera lens. For example, when flying over a square building, as an observer passes directly over it, he or she would see just the top of the building as a square underneath the observer""s feet. In filming the same scene, it is important to choose the lens and camera position to record the same images as would be seen by a human observer. For example, if the building were filmed at an angle relative to an observer, it would appear to look unrealistic on the film; a viewer of the captured image would see the sides of the building underneath his feet. The building would appear to be tilted. It would not appear to be in its correct position. The observer would get the feeling that he or she was looking at a movie projected on a screen rather than having an immersive experience. The goal for both the filming of the scene and its projection is to substantially duplicate to the eyes of a theater viewer what a human observer would have seen as he or she was physically flying over the scene. Therefore, the image shot must capture the fields of view and angles of view of a human observer flying over the scene, and the image projected on the screen must also replicate these fields of view and angles of view of the images. In other words, the objects in the physical scene that are recorded on camera must be projected onto the screen to appear to be in the same positions as the actual objects were relative to the observer (camera lens) and relative to the other objects in the scene, in order that they look correct to a viewer. The relative sizes should be approximately the same, and the relative angles of view of the projected images as seen by a theater viewer (viewing angles) should approximately match the relative angles of view of the physical objects seen by the camera lens (scene angles).
An example will now be described. Imagine a horizon at a distance, like the ridge of a hill, and a group of riders on top of the horizon on horseback. To the camera lens, the horizon appears at eye level. To appear real when projected, the horses and riders should be at the same horizon level, namely at the viewer""s eye level. If they were lower down on the screen, it would appear to a viewer that the horses were on their sides. Unless the effect is substantially fully accomplished, the observer will not feel that he is in the scene, as a part of it. In contrast, in a normal movie theater, an observer is looking at an essentially flat screen. If in the scene a character is standing on the top of a building, and a camera replaces the character that then looks down, the camera shoots down and the observer will see the traffic below. He will understand that the character is looking down, but the observer will not perceive the realistic feeling that the observer himself is on top of a building looking down. The latter effect is one of the objects of the invention.
In order to achieve the feeling of being in the scene and actually on top of the building, there are limited options. One way of accomplishing this is through CGI, computer generated images, which is a mathematically intensive and expensive process. The images can be generated entirely by the computer, or images captured on film may be manipulated to correct angles of view and sizes. One goal of the invention is to accomplish this result without the need for a significant amount of costly computer image correction. An example of a problem to be solved can be described as follows. If an observer saw a straight line in the distance, such as a road, railway track or the Golden Gate Bridge, when it appeared on the curved screen it must appear straight or flat as well. It could not appear to be curved, which is the normal result when projecting down onto a curved screen.
One aspect of the solution is to keep the projector horizontal to project straight onto the curved screen, but offset the lens downwards. This moves the image down without introducing a tilt. Moving the image down while maintaining a straight horizon is essential to compensate for the fact that the projector is above the audience. If the projector were actually in the audience""s sweet spot, then this displacement of the projector lens would not be required. However, it is impractical to place a large IMAX type projector into the center of an audience, because it would be intrusive and detract from the experience of the audience. If the projector were set at an angle by tilting the projector downward to fill the screen surface, a viewer in the audience would see a curved horizon line reflecting the angle of tilt. In other words, a horizon line would be curved as in a smiley face icon, or it could be a frowning face, depending on the relative positions of the projector, audience and screen, and whether the line is above or below the horizontal centerline of the audience. By keeping the projector lens substantially horizontal, the horizon line will project as a straight line on the curved surface. The image is lowered down by offsetting the lens downward to bring the horizon line, or any other desired line, down to a position that matches the position of that line as it was observed by a camera lens and recorded on film. In this way, the viewer suspended above a dome, or other curved surface, in a theater will see the same image as observed by a camera lens, from the same viewpoint as the camera lens, without the need to resort to computer generated imaging correction.
The curved screen is made of perforated panels, preferably aluminum, which are assembled into a generally hemispherical shape. Individual panels overlap approximately one inch, with a strip of black tape placed between the panels to ensure uniform reflectivity. Special consideration is given to the construction of the screen and the manner in which the individual panels are overlapped. If the edge of a panel can be seen by a viewer, this can, in some scenes, be observed as a black line on the screen, detracting from the overall realism of the projection. Therefore, panels are placed in such a way that panel edges are facing away from the viewer. Additionally, during the process of shearing, especially with aluminum sheets, the shearing results in a panel with a natural chamfer. If this chamfer is positioned on the outer edge of the seam, the edge thickness is reduced, further reducing the problem of a visible edge.
Aerial scenes, which are projected on the curved screen, are preferably filmed with an IMAX 15-perforation 48 fps 70 mm camera, using a Zeiss 30 mm fisheye lens. In the preferred embodiment, the camera and associated equipment are positioned underneath a helicopter in a cradle. To achieve for the viewer an impression of immersion in the projected scene, as the helicopter is flown relative to the ground, the camera and lens is pointed straight ahead. This gives the feeling of flying over the ground, whereas tilting the camera gives the impression of flying into the subject. The angular and relative positions of the filmed objects are essentially duplicated, as seen by a viewer, by the projection system. INVENTION SUMMARY
The present invention is directed to the field of recording images and projecting the recorded images onto a surface located generally below a viewer. The surface is generally curved, and may be the interior of a segment of a dome. During recording of the images, the camera lens longitudinal axis is maintained in a substantially horizontal orientation. During projection, the projector lens longitudinal axis is maintained in a substantially horizontal orientation, and the image is positioned on the surface by horizontal and/or vertical movement of the projector lens relative to the film. The image is projected to appear to the viewer to be in substantially the same position as it was to the camera lens during recording.